Unbelted drivers and passengers can cause fatal injuries to others who ride with them

Drivers or passengers protected by seat belts are at increased risk for fatal injuries if others who ride with them fail to wear their seat belts. Car occupants can be killed after being struck by other passengers who were catapulted forward, backward or sideways in a car crash.

These findings are the result of new research at the Harborview Injury Prevention and Research Center. “Car Occupant Death According to the Restraint Use of Other Occupants: A Matched Cohort Study” is published in the Jan. 21 issue of the Journal of the American Medical Association.

The researchers studied more than 70,000 motor vehicle that crashed between 1988 and 2000. The researchers found that the risk of death was 20 percent greater for a belted person in front of an unrestrained rear passenger, compared with a belted person in front of a restrained rear passenger. The risk of death for a rear occupant was increased about 22 percent if someone in front was unrestrained, compared with having someone in front who was restrained.

“Prior studies have shown that wearing a seat belt decreases the risk of fatal injury by about 60 percent,” says Dr. Peter Cummings, a University of Washington professor of epidemiology and principal investigator for the study. “Our research shows that if you’re a driver or passenger, your chance of dying is reduced if everyone else in the car is also wearing their seat belts. In some crashes an unbelted occupant can become a missile that can strike and kill another person in the same car.”

The researchers studied data from the National Highway Traffic Safety Administration, including crashes involving passenger cars of model years 1975-2001. The study was supported by grants from the Centers for Disease Control and Prevention and by the Crash Injury Research and Engineering Network of the National Highway Traffic Safety Administration.

In addition to Cummings, the study was conducted by Dr. Frederick Rivara, a University of Washington professor of pediatrics and adjunct professor of epidemiology.